Over-Potential Tailored Thin and Dense Lithium Carbonate Growth in Solid Electrolyte Interphase for Advanced Lithium Ion Batteries

A stable solid electrolyte interphase (SEI) is highly desired to prevent parasitic reactions during normal operation of lithium-ion batteries (LIBs). Lithium carbonate (Li₂CO₃) is one of the most significant components for smooth SEI passivation layers; while the formation mechanism and special distribution of the Li₂CO₃ layer has not yet been illustrated. Here, an over-potential tailored Li₂CO₃ growth mechanism based on the typical hard carbon anode is demonstrated. With an increase in the over-potential, the size of Li₂CO₃ decreases gradually as the amount increases. When the over-potential is large (potential at 0.01 V), a Li₂CO₃-rich thin and dense inorganic layer with the average thickness of 4.4 nm in the SEI is constructed. The special SEI the completely wraps the boundaries of the anode enables a larger Li-ion de-solvation energy barrier and a lower Li-ion diffusion energy barrier, which supports low self-discharge behavior and a fast kinetic rate at the anode. More generally, this Li₂CO₃ growth mechanism is also applicable to commercialized graphite anodes and similar results are also obtained. Therefore, this work provides a new insight into the Li₂CO₃ growth mechanism in SEIs, as well as a guideline for the design of stable artificial SEIs.